The present invention relates to a spring intended especially for making an electrical connection. Such a connecting spring is found, for example, in a connection terminal for an electrical conductor.
It is known practice for springs to be used to hold the end of a stripped conductor against a current-supply rail in a connection terminal. Documents DE-37 27 091 and DE-42 37 733 for example describe connection terminals of this type. These documents disclose a connecting spring made of a flat elastic material and exhibiting the general shape of a loop. The connecting spring has a pressing branch intended to rest against the current supply rail and a gripping branch folded from the rear part of the spring and running more or less transversely to the current supply rail, and also an elastic arc connecting the rear part and the pressing branch together from behind.
A device of this type may also be used for making an insulation-displacement connection of an electrical cable. In this case, the spring is used to store up the energy needed to displace the insulation of an electrical cable and trap it in a connecting slit, and to restore this energy at the appropriate time.
A spring such as this has, on its gripping branch, a window through which the current supply rail passes, and which also accommodates the end from which the insulation has been displaced of a conductor that is to be connected. This conductor is held against the current supply rail, on the opposite side to the side against which the pressing branch rests.
In connecting springs which exist at the present time, this window has a rectangular shape. Its width, which has an influence on the maximum connectable cross section, is constant. In addition, this width is limited by the mechanical integrity of the spring. What happens is that widening the window weakens the gripping branch of this spring.
The object of the present invention is to provide a connecting spring which, for an identical size to that of the springs of the prior art, makes it possible to connect a conductor of larger diameter, while at the same time maintaining good mechanical properties.
To this end, the invention proposes a spring, particularly a connecting spring, made of an elastic leaf bent in such a way as to exhibit a pressing branch and a moving branch which are connected by an elastic arc to the pressing branch, an opening being made in the moving branch near its free end and being intended to accommodate an end of the conductor that is to be connected.
According to the invention, the opening transversely has a variable width, this width being greater at the end nearest the free end of the moving branch.
In this way, it is possible to connect conductors of relatively large diameter. The conductor is therefore introduced at the end where the opening is widest. This widest region, which corresponds to a smaller cross section of material, is made in a region in which the mechanical stresses are not very high when the spring is stressed. Thus, it is possible to provide a width of opening greater than the width of the opening generally made in a connecting spring of the same size in the prior art.
In one preferred embodiment, the opening has an elongate trapezoidal shape. In this case, the large base of the trapezium is of course at the end nearest the free end of the moving branch of the spring.
In another embodiment of a spring according to the invention, the opening exhibits two regions of different widths, connected by a connecting region. A preferred alternative form envisages for the connecting region to have a contour in the form of an arc of a circle and is arranged in such a way that a conductor corresponding to the maximum connectable diameter hugs the contour of the connecting region when it is introduced into the opening. This alternative form of embodiment makes it possible to optimize the mechanical strength of the spring at its moving branch.